Frame Summing Selector Dialog

This dialog allows you to control the saving of either intermediate frames from a Falcon camera or variably-sized sums of frames from a K2 camera. 

For the Falcon camera, an exposure consists of a certain number of readouts at a fixed interval, referred to here as camera frames.  The intermediate frames that get saved are sums of successive sets of camera frames.  The controls in this dialog let you select which camera frames are summed and saved, and this is the only way to set the exposure time integrated in the saved frames.

For the Falcon 3 camera, when alignment in the Falcon processor is selected for this parameter set, the constraints for alignment are imposed as changes are made here.  Specifically, a minimum exposure time is maintained, depending on whether linear or counting mode is selected; and the summed frames are constrained to either a single camera frame or a multiple of 6 frames.  The only way to switch to saving single camera frames is to type one line with the total number of camera frames and a 1 into the box for the list of frame sums.  Once single-frame saving is specify, it should be maintained as you change exposure time.  Similarly, the only way to switch back to multiples of 6 is to type in a line with some number of summed frames and a 6.

For the K2 camera, the exposure time of the camera frames available for saving can be set in the main camera setup dialog, and this dialog is needed only if you want to save frames with different durations from a single exposure.  In this case, the stack of images prepared by DigitalMicrograph at the selected frame time will be referred to as camera frames, and the sums saved by the SerialEMCCD plugin are referred to as summed frames.  Note that DM's lengthy time to prepare the camera frames is proportional to the number of camera frames, so the total time for saving the data will reflect primarily this number rather than the number of summed frames saved.  If you want to sum numerous camera frames from later in the exposure, it may be significantly faster to take two separate exposures with different frame times.

An unequal distribution of camera frames among the summed frames, i.e., variable frame durations, is created by typing the actual distribution into the large box at the bottom. The box is formatted to hold a pair of numbers on each line.  The first number of a pair is the number of successive summed frames of a particular duration; the second number is the number of camera frames in each of those summed frames.  The program will remember whatever distribution is imposed when you enter such numbers or change the values in the list.  Thereafter, when you change other items in the dialog, the program will reapportion camera frames among summed frames so as to maintain this distribution. In fact, even when this dialog is not open, changes in exposure time or frame time will cause the program to reapportion camera frames, provided that frame summing is enabled.  Note that whenever a given number of camera frames does not divide equally among a set of summed frames, the extra camera frames will be added to the later summed frames in that set.

Exposure time

This text box is initialized with the current exposure time for this parameter set, but the time can be changed here.  The exposure is constrained to be a multiple of the camera frame time.  For the Falcon 2, the total number of camera frames in the exposure is the sum of ones selected to be skipped at the beginning and end and the total included in the saved frames.  When this time is changed, a new number of camera frames is distributed among the current number of summed frames.

Camera frame time

For the K2, this text box contains the current frame time for the parameter set, which can be changed here.  When the time is changed, the exposure is kept constant and a new number of camera frames is distributed among the current number of summed frames.

Below this entry is a display of the minimum and maximum summed frames times implied by the current entries for frame summing.

Number of frames to save

Use this spinner to select how many summed frames to save from the exposure.  Changing this value will generally cause the same total camera frames being saved to be distributed among a different number of summed frames.

Skip before start

For the Falcon 2, use this spinner to set whether to leave out any camera frames at the beginning of the exposure, which may have shuttering effects.  Changing this value will change the exposure time.  For Falcon 3, the first and last frames with shuttering effects are automatically discarded.

Total to save

This spinner reflects the the total number of camera frames that will be included in the saved frames.  Changing this value will increase the exposure time.

Skip after end

For the Falcon 2, use this spinner to leave out camera frames at the end of the exposure; such camera frames may also have shuttering effects.  Changing this value will change the exposure time.

List of frame sums

The format of this text box was explained above.  Be aware of these points: 1) Type Tab or click elsewhere in the dialog to have the program read your changes.  The program will not process your changes until you do this, so you need to make a complete and consistent set of changes before doing so.  2) There must be at least two numbers on each line, and numbers after the second one are ignored.  3) The program will rewrite the list into the box after you change it.  4) Thus you can simply add a new second value on a line without erasing the existing one yourself.  5) Changes here will affect exposure time and number of saved frames and camera frames.

Equalize

Use this button to eliminate whatever unequal distribution of camera frames has been imposed by typing into the list.  This is useful for the Falcon, but for the K2, simply disable saving summed frames instead.